Electric conductor



Oct. 20, 1931.. c. F. OBERMAIER 1,828,614

ELECTRI C CONDUCTOR Filed March 10, 1926 rn/ent or Carl F Obermaie l His Attorn ey.

. tion.

Patented Oct. 20, 1931 UNITED STATES PATENT OFFICE CARL F. OBERMAIER, OFYORK, PENNSYLVANIA, ASSIGNOR TO GENERAL ELECTRIC COMPANY, A CORPORATIONOF NEW YORK ELECTRIC CONDUCTOR Application filed March 10, 1926. SerialNo. 93,712.

My invention relates to electric conductors,

and has for its object the provision of a flexible multiple electricconductor.

My invention relates in particular to the multiple conductor cords usedwith electrically heated appliances, such as flatirons, and the like.Such multiple conductor cords consist of a plurality of insulatedconductors, usually two, which may be and usually are twisted, and boundtogether by an outer fabric sleeve. NVhen the insulated conductors arethus secured together it will be ob; served that there is substantiallycontinuous linear contact between them, which comparatively large areaof contact gives a very appreciable amount of friction thereby offeringa considerable impediment to slippage of the conductors with relation toeach other when the cord is bent. This results in impairment of theflexibility of the multiple conductor cord as a whole. Furthermore, ifthe conductors be twisted together tightly or the outer fabric sleeveapplied tightly the friction between the conductors will be increasedand the flexibility of the cord corres ondingly impaired.

11 carrying out my invention, I wrap a cord lielically around one of theinsulated conductors throughout its full length, the turns of this cordbeing widely spaced, whereby point contact is provided between theconductors. This decreases the friction between the conductors andprovides for a corresponding increase in flexibility of the multipleconductor cord.

For a more complete understanding of my invention reference should behad to the accompanying drawing, the single figure of which is afragmentary view of an insulated electrical conductor embodying myinven- Referring to the drawing, I have shown my invention in one formas embodied in a twisted twin conductor cord, such as often used forelectrical appliances and thelike, although it will be understood thatmy invention has applicationto various kinds of electrical conductorcords. The conducting cord comprises two copper conducting wires 10 and11 which for the purpose of giving them greater flexibility are made upof a plurality of small copper wirs either bunched, stranded or braided.Various flexible insulations may be used for the con ductors 10 and 11,although as shown an electrically insulating layer or wrapping 12 ofasbestos cords or threads is first applied directly to the copperconductor. This layer consists of a plurality of tightly twistedasbestos cords 13 which are wrapped together around the wire and lieside by side. As shown, several of these threads or cords are wound onthe conductor simultaneously, the cords, it will be understood, passingaround and around the conductor in helical formation, as shown in thedrawing. The cords, lying side by side, form in effect a band which isWrapped on the conductor. This wrapping of asbestos cords is secured tothe conductor and the turns of the cords held rigidly in place by meansof an outer layer of felted asbestos 14 which is applied directly overthe cords.

Any suitable apparatus may be used for apsulating covering. This cordpasses around the insulated conductor in an open helix, the turns beingspaced a suitable distance apart and as shown are quite widelyseparated. As shown the cord 15 consists of a pair of strands lying sideby side. The two insulated conductors may be and usually are twistedtogether and secured in this relation by means of an outer sleeve 16 ofbraided fabric threads, such as cotton or silk.

It will be observed that the two insulated conductors are twistedtogether in such man- 0 ner that the insulated conductor lI passesaround the insulated conductor 10 in a direction opposite to the cord15. It will also be observed that the spacing of the turns of the cord15 is approximately half the spacing of the .turns of the conductors 10and 11 so there are two turns of the cords 15 to every turn of theconductors 10 and 11.

The cord 15 has the effect of slightly separating the two insulatedconductors so that the otherwise continuous linear contact between thetwo conductors is broken up into a plurality of point contacts with thecord 15. The point contacts result in much less friction between the twoconductors and consequently reduce the impediment to relative slippageof the conductors when the twin conductor cord is bent. The flexibilityof the cord as a whole is thereby increased.

'While I have described my invention as embodied in concrete form and asoperating in a specific manner in accordance with the provisions of thepatent statutes, it should be understood that I do not limit myinvention thereto, since various modifications thereof will suggestthemselves to those skilled in the art without departing from-the spiritof my invention, the scope of which is set forth in the annexed claims.

What I claim as new, and desire to secure .by Letters Patent of theUnited States, is:

l. The combination with a multiple conductor cord comprising a pluralityof insulated conductors, of an attenuated flexible mernber wrappedaround one of said conductors so as to reduce the friction between saidconductors and thereby increase the-flexibility of the cord, and anouter covering surrounding said conductors.

2. The combination with a plurality of insulated conductors, of a cordof fibrous material wrapped helically around one of said conductors soas to reduce the contact area between said conductors and therebyincrease their flexibility, and an outer fibrous cover-- ing surroundingsaid conductors.

3. A flexible electric heater cord comprising a pair of insulatedconductors twisted together, an outer fibrous covering securing saidconductors together, and a cord of fibrous material wound helicallyaround one of said conductors.

4:. A flexible heater cord comprising a pair of stranded conductors,electrical insulation on each of said conductors, said conductors beingtwisted together, a cord of fibrous material wound helically around oneof said conductors, and an outer fibrous covering surrounding saidconductors so as to secure them together.

In witness whereof, I have hereunto set my hand this 8th day of March,19:26.

CARL F. OBERMATER.

